A wireless communication system is widely used to provide various types of communication. For example, voice and/or data are provided by the wireless communication system. A typical wireless communication system provides one or more shared resources to multiple users. For example, the wireless communication system may use various multiple access schemes, such as code division multiple access (CDMA), time division multiple access (TDMA), and frequency division multiple access (FDMA).
Orthogonal frequency division multiplexing (OFDM) uses a plurality of orthogonal subcarriers. Further, the OFDM uses an orthogonal property between inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT). A transmitter transmits data by performing IFFT on data. A receiver restores original data by performing FFT on a received signal. The transmitter uses IFFT to combine the plurality of subcarriers, and the receiver uses FFT to split the plurality of subcarriers. According to the OFDM, complexity of the receiver can be decreased in a frequency selective fading environment of a broadband channel, and spectral efficiency can be increased by using selective scheduling in a frequency domain by utilizing a different channel feature between subcarriers. Orthogonal frequency division multiple access (OFDMA) is a multiple access method based on the OFDM. According to the OFDMA, different subcarriers are allocated to multiple users, and thus efficiency of radio resources can be increased.
For the purpose of data transmission/reception, system synchronization acquisition, channel information feedback, etc., there is a need to estimate an uplink channel or a downlink channel in the wireless communication system. Channel estimation is a process of recovering a transmission signal by compensating for signal distortion in an environment where a rapid change occurs due to fading. In general, channel estimation requires a reference signal or a pilot known to both the transmitter and the receiver. In a multiple antenna system that increases data transmission efficiency by using a plurality of antennas, each antenna experiences a different channel, and thus a pilot arrangement structure is designed by considering each antenna. Channel estimation can become more accurate when more pilots are arranged in a limited radio resource. However, as more pilots are arranged, the radio resources capable of transmitting data is decreased. Therefore, a data throughput of the wireless communication system is decreased.
Accordingly, there is a need for a pilot transmission method capable of decreasing an overhead caused by a pilot and increasing a throughput of a wireless communication system.